Alternating current welding apparatus



. Sept 7 1937- c. N. MITCHELL 2,092,003

ALTERNATING CURRENT WELDING APPARATUS Original Filed Nov. 24, 1930 5Sheets-Sheet 2 PHASE -X H- *PHAsE-Y L-PHASE- z .32 3 f NVENTOR.

ATTORNE f77/y a.

Sept. 7, 1937. c. N. MlTci-IELL 2,092,003

ALTERNATING CURRENT WIELDING APPARATUS Original Filed Nov. 24, 1930 3Sheets-Sheet 3 72 ENToR.

73 C ourney NIW/tdw A TT ORNE V5.

Patented Sept. 7, 1937 UNITED STATES PATENT OFFICE Courtney N. Mitchell,Strongsville, Ohio Application November 24, 1930, Serial No. 491,627Renewed May 29, 1936 .29 cams. (ci. zia-s) This invention, relating asindicated, to a method of and apparatus for electric welding by means ofalternating current is in part a continuation of application Serial No.430,694 illed Feb. 24,

1930, in that the general arrangement of the apparatus disclosed in theaforesaid application is employed in carrying out the principles of thisinvention, changes being made only in the specific features comprisingthe novel elements of this method and design. As will be noted from acareful examination of the apparatus disclosed in the aforesaidco-pending application, such apparatus is designed primarily for thepurpose of welding tubing and the like having a relatively l5 thin shellor wall, so that the contiguous edges of the seam to be welded are ofrelatively thin material. One of the objects of this invention is toprovide an apparatus which may be efliciently employed for the purposeof welding ma- 20 ter'ialwhich is much thicker than any capable of beinghandled by the apparatus disclosed in said application.

In the welding of tubing and like material at a relatively high speedconsiderable difficulty 25 has been experienced in the past inmaintaining the proper contact between the welding electrode and theedges of the seam to be joined. This difficulty has been due primarilyto the fact that as the metal along the seam to be welded is heat- 30 edsufficiently to properly weld, the pressure nec-v essarily exerted onsuch material to effect the weld by means of the contacting electrodesor rollers has been sufficient to deform such material and further, dueto the fact that such material 35 may be deformed unevenly, theelectrode will upon relative movement of the article to be welded haveonly superficial contact with portions of ,the tube or like articles. Itis among the objects of this invention to provide a method 40 andapparatus which shall obviate this undesirable characteristic of weldingapparatus and methods as heretofore employed.

As is well known to those familiar with the art of electric welding, oneof the main sources of deterioration of the material forming the weldjoining the two elements sought to be united, has been the oxidation ofthe highly heated metal, which oxidation will prevent the formation of ahomogeneous weld structure, and a consequent 50 weakness thereof. Afurther source of deterioration of the resultant Weld has been due tothe *5 combination of atmospheric nitrogen with the molten or highlyheated metal to form objectionable iron nitrides which have the samedeleterious 55 eiect as the oxides formed by the combination meanshereinafter oi' the oxygen with the heated metal. It is among theobjects of my invention to provide a method and apparatus foralternating current electric welding which will produce a finished weldseam having none of the hereinbefore described struc- 5 turalweaknesses.

As is well known to those familiar with the art of alternating currentelectric welding the individual welds across the seam cleft are producedby the successive impulses, both positive and neg- 10 ative, of thealternating current. The employment of alternating current for thepurposes of welding in the fashion described in the aforesaid co-pendingapplication results in an infinite number of separate welds usuallyreferred to as stitches, which, by employing the apparatus comprising myinvention are so related as to be contiguous or overlapping so that acontinuous weld results. When alternating current is employed forwelding purposes, one of the objectionable features of its use has beenthat the maximum of the impulse necessary to produce the weld has beenexcessive to the point where an overheating and consequent deteriorationof the metal has resulted. This will be more readily understoodby havingreference to the common sine wave form of alternating currentusually'employed wherein the positive and negative impulses of currentoccur in relatively sharp peaks. This common sine wave form ofalternating current has caused a burning of the metal without asuilicient duration of the welding current impulse to form a weld orstitch of appreciable length. It is among the objects of my invention toprovide a method of electric welding by alternating current which shallhave none of these undesirable characteristics. Other objects of myinvention will appear as the description proceeds'.

To the accomplishment of the foregoing and related ends, said inventionthen, consists of the 40 fully described and particularly pointed out inthe claims. K The annexed drawings and the following description settingforth in detail certain mechanism embodying the invention, suchdisclosed means constituting however, but one of the various mechanicalforms in which the principle of the invention may be used.

In said annexed drawings: y

Fig. 1 is a part sectional, part side revational view of one form of theapparatus comprising my invention; Fig. 2 is a transverse sectional'view of the apparatus illustrated in Fig. 1; Fig. 3 is a fragmentary,part sectional, part elevational view oi' the welding electrodes and thetube to be welded thereby prior to the occurrence of the gaged nut ofmaintaining the rollers in proper assembled.

welding current impulse across such electrode; Fig. 4 is a, broken,fragmentary, part sectional, part elevational view of the tube to bewelded and a portion of the associated mechanism for accomplishing thewelding operation; Fig. 5 is a wiring diagram -of the circuits designedto supply the welding current to the apparatus illustrated inl theprevious figures; Fig. 6 isa diagrammatic representation of the weldingcurrent and the separate currents of different frequencies employed toproduce the resultant welding current; and Fig. 7 is a transversesectional view of an apparatus similar to that illustrated in theprevious gures, but designed for the purpose of accomplishing thewelding operation by the incorporation of a filler element of suitablematerial in the welded seam.

Referring more specifically to the drawings, and more especially toFigs. 1 and 2, the apparatus here illustrated, it will be noted, isSimilar to that illustrated and described in the aforesaid copendingapplication, and consists of side frame members I which extendlongitudinally of the apparatus and are cross braced at their ends byweb members such as 2 to lconfine and support the welding apparatuspresently to be described. Situated within the frame comprising the sidemembers I and theend frame members 2 arela plurality of separate weldingunits, each of which is designed to produce a separate weld of thecontiguous edges of' the seam cleft in the tube or like article passingtherethrough, so that by a proper arrangement of such separate weldingunits and a correlation of therelative positions of such units with thespeed of the tube or like article passed therethrough, the individualunits may be crossed` to occupy contiguous or slightly overlappingrelations.

Each of the above referred to separate welding units consists ofelectrode holder blocks 3 which have apertures extending transverselytherethrough adapted to receive blocks of insulating material 4 whichare secured in such apertures by dowel pins 5. The blocks of insulatingmaterial 4 are centrally apertured to receive supportingY rods or bars 6which are terminally anchored in brackets 'I secured to the end framemembers 2. The bars 6 therefore support the electrode holder blocks 3intermediately of the side-frame members I. The electrodeholder blocks3are maintained in proper adjusting relationship axially of thesupporting rods 6 by adjusting rods such as 8 which threadably engagesupporting bracket members 9 respectively secured to but insulated fromsuch welding electrode supporting blocks 3. One bracket such as 9 andone adjusting rod such as 8 are required for each set of blocks such as3. and with the rods 9 secured to the end members each individualwelding unit may be properly adjusted relative to the others for the-purposes hereinbefore explained. Each of the blocks 3 is provided witha depending `portion I0 formed integrally therewith and provided with asubstantially rectangular aperturel II in which is positiponed a bearingblock I2. I2 have journaled therein the necks I3 of electrode rollersI4. The electrode rollers I4 have positioned intermediately thereof aspacing member I5 of insulating material, and such rollers and theirassociated necks are maintained in proper assembled relation by atubular member I6 provided with a circumferential shoulder I1 at oneend, and at the other end with a threadably en- I8 which is employed forthe purpose The bearing blocks `welded displaced relation on thetubularmember I 6. The electrode rollers I4 and the tubular member I6are insulated by means of sleeves I9 which arel likewise provided withcircumferential flanges on the terminals thereof to prevent contact,between the ange I1, the nut I8 and the hub I3 of the rollers I4.

The bearing blocks I2 and consequently the electrode rollers I4supported thereby are resiliently maintained in contact with the bottomof the aperture II in which such bearing blocks are mounted by means ofcompression springs 20 suitably mounted in the blocks 3. The bearingblocks I2 may be adjusted vertically in the aperture II in which. thesame are mounted against the resilient action of the springs 26 by meansof adjustlng screws 2I for the purposes hereinafter more fullyexplained. The blocks 3 are resiliently maintained in intimate contactwith the electrode rollers I4 by means of compression springs 22supported in the side frame members I by means of tubular screw elements23.

The terminals of the tubular members I6 are provided with sphericalseats 24 which engage the complementary seats formed on the ends offluid supply conduits 25 resiliently supported in the side frame membersI by means of springs 26 and tubular screw caps 2'I. Suitable members ofinsulating material such as 28 are interposed between the ends ofthetubular member I6 and the members 25 so that the electrode holders I4will be properly insulated vfrom each other in order to carry out thewelding operation. 4Fluid conduits such as 29 are provided with members25 so that a suitable cooling iiuid may be caused to circulate throughthe tubular member I6 and through the radially extending apertures 30into the space defined by the annular recesses formed on the juxtaposedfaces of the electrode rollers I4.

Thel tube or like element 3I is supportedvin proper relation to thewelding electrode rollers I4 by means of a backing roller 32 which isrotatably mounted on a shaft 33. The shaft 33 is supported at one end bya hinged bracket 34 secured to one of the side frame members I-and suchshaft is sllpported at its other end by a bracket 35 removably securedto the other of such side frame members by means of a bolt 36. This formof mounting for the roller 32 permits such roller to be replaced byanother ofl a diierent diameter as the same becomes worn or due to therequirement of a diierent size roller for backing up a dierent size ofpipe to be welded, by simply removingv the bolt 36 and moving the shaft33 in a clock-wise direction about its point of pivotal support in thehinged bracket 34 until the roller 32 can be moved axially from theshaft. Weld'- ing current for the electrode rollers I4 is suppliedthrough leads 31 and 38 respectively secured to the blocks 3 supportingsuch rollers and also connected to opposite sides of the line formingthe source of welding current supply hereinafter moreh fully explained.l

As indicated at the outset of this description, as the tube or likearticle is caused to move through the welding apparatus the successiveWelds made therein by the separate welding units may cause depressionsin the surface of the tube so that poor contact will be had by theWelding electrodes unless some means is provided to insure positivecontact. As most clearly illustrated in Fig. 3 the tube, preliminary tothe welding operation is formed with a contour not truly symmetrical butend portions 39 adjacent the'seam to be radially for a short distance,so

that as the electrode rollers I4 pass thereover under the influence ofthe 'compression springs 20, the heat generated by the impulse ofwelding current flowing across the seam 40 will heat the metal in theportion 39 sufficiently so that the springs 26 will cause the roller I4to form the tube into truly cylindrical cross section.

In order to obviate the occurrence of an inferiorweld resulting from thecombination of the heated metal with the atmospheric oxygen or nitrogenas hereinbefore described, I propose to provide a blanket of inert gasaround the welding area so as to exclude all atmospheric oxygen andnitrogen. This is accomplished as most clearly illustrated in Figs. land 4 by providing a. tubular member such as 4I extending axially intothe tube to be welded and provided with a plurality of egress apertures42 positioned directly beneath the electrode rollers I4 so that theinner surface of the pipe or tube in the welding area will be suitablyblanketed by such inert gas supplied by the tube 4 I In order to preventthe escape of the gas from the tubeI and further to increase theefficiency of the apparatus a gasket member such as 43 may be applied tothe end of such tube to prevent the escape of inert gas at this point.Likewise, the blanket of inert gas may be supplied to the exterior ofthe tube in the areas to be welded by 'nozzle members such as 44supplied with the inert gas used for the above described purposes byconduit members such as 45, the nozzles 44 being directed to the weldingarea directly beneath the electrode rollers I4. In order to prevent theuse of unnecessary quantities of such inert gas, and

further, to generally increase the efciency of the apparatus comprisingmy invention, I may provide cross members such'as 46 and 41 respectivelyclosing the bottom and top of the space laterally confined by the sideand end frame members l and 2. In order to facilitate the observation ofthe welding operation, the cover member 41 across the top of theapparatus may be provided with an aperture 46 closed by a transparentcover member 49.

It will be noted that the above described apparatus is primarilydesigned to be employed for the purpose of welding tubing wherein asimple so-called butt weld is effected. If, as is sometimes desirablefor certain classes of Work, it

should be desirable to supply a strip or filler element of foreignmaterial such as a wire to the seam to be welded, the apparatus toaccomplish this result is most clearly illustrated in Fig. 7. Thegeneral form of this apparatus is similar to that described in theprevious figures, and here again, consists of side frame members 56,intermediately of which are supported in proper relation electrode`supporting blocks l provided with recesses for blocks of insulatingmaterial which receive supporting rods 52 which are anchored at theirends in the members 53 extending transversely of the side frame members.The plurality of separate welding units are in this form of constructionsupporting in proper spaced relation axially of the supporting rods 52by rods 54 which are similar in their operations and mounting to therods 6 as described in connection with the previous figures. Theelectrode supporting blocks 5| have journaled therein elec.- troderollers 55 which are provided with axially extending necks 56 rotatablysupported in sleeves of insulating material 51 carried by the blocks 5|.'Ihe electrode roller 55 is provided with a spherical circumferentialgroove 56 which will contact with the outer periphery of the tube 59 tobe welded. The tubular necks 56 of the electrode rollers 55 areterminally provided with spherical seats 60 engaged by the complementaryterminals 6I of uid supply members 62 which are resiliently maintainedin contact with the terminals of the necks 56 by means of springs 63 andscrew cups 64 secured in the side frame members 56. Elements ofinsulating material 65 are interposed between the juxtaposed terminals50 and 6|, so that no welding current may stray in this direction. Thecooling fluid for the electrode rollers 55 is supplied by means ofconduit such as 66 secured to the ends of the members 62. The tube to bewelded is supported by means of rollers 68 and 59, the former beingmounted on stub shafts and the latter on a shaft 1I,- all of such shaftsbeing carried by a block 12 secured to the end frame members 53 byshafts 13. One lead 14 for the welding current is secured to the block5l supporting the electrode rollers 55 and the other lead is secured tothe block 12 supporting the backing rollers 68 and 69. The seam cleft inthe tube 55 to be welded is, as above indicated, supplied Ywith a strip59 of metal which will be interposed between the edges of such seam sothat as the welding of the same progresses the wire or like material 59'will be heated by the currentv .flow therethrough, which, when broughtinto intimate contact with the similarly heated edges of the seam cleftof the pressure of the springs maintaining contact between the roller 55and the tube, the parts will be welded together. As indicated at theoutset of this description, instead of employing regular sine wavealternating current in connection with the method and apparatuscomprising this invention, I propose to employ a current of modifiedwave form such as is illustrated by the line C in Fig. 6. Bysuperimposing a high and low frequency such as is illustrated bythelines A and B in Fig. 6 on the welding current circuit the resultantwelding current will have the form illustrated by the curve C. Assumingthat the high frequency current is 60 cycle current and the lowfrequency is 20 cycle current. by a proper regulation of the magnitudeof each of such currents, the form of the resultant current wave cyclemay be controlled. This form of welding'current, as illustrated by thewave lin-e C eliminates the objectionable peak of the regular sine waveform of current, which peak, in order to produce a stitch or weld ofappreciable length would cause suillcient current to flow across theseam cleft to heat the metal to such a point that deterioration thereofwould occur. It will be noted in connection with the current wavediagram as illustrated in Fig. 6 that the wave line C may be soregulated that any desired contour thereof may be had to adapt the' sameto the particular requirements of the material to be welded. One of themeans for producing the modified welding current wave illustrated inFig. 6 is shown by the wiring diagram in Fig. 5. In this figurethe-transformers 16, 11 and 1,6 are each provided with superimposedprimary windings 19 and 60 which are respectively secured across thethree-phases, i. e. X, Y, and Z of a high frequency line, and X', Y' andZ of a low frequency line. The secondary windings 6l of the transformers`16, 11 and 16 are in turn connected across the electrode rollers I4which contact with the tube 3l to be welded along opposite sides of theseam. It will be noted that a different arrangement than thatillustrated in this figure may be employed for the purpose of producingthe modified Wave cycle to the welding current and also that a greaternumber of transformers may be employed in order to supply the weldingcurrent to more than the three illustrated pairs of welding electrodes.It is believed that the advantages of this modied wave form ofalternating welding current has further advantages so apparent to thosefamiliar with the art that a repetition of this is unnecessary.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any of the followingclaims or-the equivalent of such stated means be employed.

I therefore particularly point out and directly claim asmy invention:

1. In apparatus for electric welding, the combination of a plurality ofpaired electrodes contacting with opposite edges of the seam to bewelded, means for introducing an inert fluid to the area being welded,said last named means comprising a nozzle directed into the area of theweld, an enclosure structure adapted to retain the aforesaid inertfluid, a pair of bars extending through said enclosure and supportingsaid electrodes, means for moving said electrodes along said bars, andmeans for advancing said seam relative the said electrodes.

2. In apparatus for electric welding tubing the combination of aplurality of paired electrodes adapted to contact with the oppositeedges of the seam to be welded, a conduit extending into said tube fordischarging an inert fluid into said tube in the vicinity of the areasbeing welded, an enclosure structure surrounding a portion of said'tube, a pair of bars extending through said enclosure and supportingsaid electrodes, means for moving said electrodes axially of said tube,and means for advancing said tube relative said electrodes.

3. In apparatus for electric welding, the combination of a plurality ofpaired electrodes, said electrodes comprising rollers for directingwelding current flow across the seam to be welded at; successive points,means associated with said rollers for supporting the work to be welded,means for advancing said seam relative said electrodes supporting barssubstantially parallel with, the seam, a supporting means interposedbetween said bars and said rollers, means maintaining said rollers lincontact with the work, a support for said last named means, and meansfor adjusting the position of said support longitudinally the seam to bewelded.

4. In apparatus for electric welding, the combination of a plurality ofpaired electrodes, said electrodes comprising rollers for directingwelding current flow across the seam to be welded at successive points,means associated with said rollersfor supporting the work to'be welded,supporting bars substantially parallelA with the seam, a supportingmeans interposed between said bars and said rollers, resilient meansmaintaining said rollers in contact with the work, and means foradjusting the position of the aforesaid rollers.

5. Apparatus for electric welding comprising a frame, a plurality ofspaced pairs of electrodes supported by said frame and adapted tocontact opposite sides of a seam to be welded, and supporting barshaving their axes substantially parallel with said seam, sliding meansinterposed between said bars and said electrodes, means forindependently adjusting the position of eachpair of electrodes alongsaid seam, said last named means comprising a screw extendinglongitudito be Welded, supporting bars having their axes I substantiallyparallel with said se'am, sliding means interposed between said bars andsaidV electrodes, and means for independently adjusting the position ofeach pair of electrodes along said seam, said last named meanscomprising a screw extending longitudinally the seam to be welded, a nutmember and an axially constrained member engaging said screw, and one ofthe last named members associated with the electrode adjusted by saidscrew and the other of said members carried by the aforesaid frame.

7. Apparatus for electric welding comprising-a frame, means for movablysupporting thematerial to be welded, a plurality of spaced pairs ofelectrodes supported by said frame and adapted to contact opposite sidesof the seam of the material to be welded, said frame including a pair ofsupporting bars having their axes substantially parallel with said seam,sliding means interposed between "said bars and said electrodes, meansfor independently adjusting the position of each pair of electrodesalong said seam, tension means for maintaining the electrodes in contactwith said material, said tension means comprising a plurality ofresilient members acting substantiallyv at right anglesto each other.

8. Apparatus for electric welding comprising a frame, means for movablysupporting the material to be welded, a plurality of spaced pairs ofelectrodes supported by said frame and in contact with opposite sides ofthe seam of the material to be welded, and means for circulating acooling fluid axially through each pair of electrodes, said meanscomprising a hollow shaft, a conduit member engaging said hollow shaft,and spring means for holding said conduit member in sealed relationshipwith said shaft.

9. Apparatus for electric welding comprising a frame, means for movablysupporting the material to be welded, a plurality of spaced pairs ofelectrodes supported by said frame and in contact with opposite sides ofthe seam of said material, a hollow conduit extending axially througheach pair of electrodes, and means for-circulating a cooling fluidthrough said conduit, said member in communication with said hollowelectrode, said conduit member having a self aligning seat, and meansfor maintaining said seat in contact with an associated part.

10. Apparatus for electric welding comprising la frame, means formovably supporting the mameans comprising a hollow electrode, a conduity prising a plurality of spring members electrodes comprising rollersfor directing welding current ilow across the seam to be Welded atsuccessive points, a supporting bar for said electrodes, universal meansinterposed between said barand said rollers for permitting movement ofsaid rollers in two directions transversely oi said seam, the twodirections being substantially at right angles to each other, meansassociated with said rollers for supporting the work to be welded, andresilient means maintaining said rollers in contact with the work, saidresilient means comassociated witheach electrode.

12. In apparatus for electric welding, the combination of pairedelectrodes contacting with opposite edges of the seam to be welded,means for introducing a fluid to the area to be welded, said meanscomprising a conduit adapted to direct the iiuid into the region of theweld, an enclosure structure surrounding the region of discharge of saidiluid, a frame for the aforesaid apparatus comprising walls for theenclosure, bars extending through said enclosure, said bars beingsupported by said frame, and means for attaching the aforesaidelectrodes to said bars.

13. In apparatus for electric welding, the combination f pairedelectrodes contacting with opposite edges of the seam to be welded,means for introducing fluid to the edges to be welded, an enclosurestructure surrounding said electrodes anda part of the. seam, saidenclosure structure adapted to retain the said uid, bars 'extendingthrough said enclosure, said bars being supported by a frame, means forattaching the aforesaid electrodes to said bars, and means connectingsaid electrodesand said frame whereby the position of said electrodesmay be adjusted.

14. In apparatus for electric welding, the combination of pairedelectrodes contacting with opposite edges of the seam to be welded,means for introducing uid to the vedges of said seam, an enclosurestructure surrounding said electrodes and a part of the seam, barsextending through the space within the enclosure structure, said barsbeing supported by a trame, means for adjustably attaching the aforesaidelectrodes to said bars, and a means for inspecting the interior of saidenclosure'structure while the said apparatus is in operation.

15. In apparatus for electric welding, a frame, supporting bars carriedby said frame, said bars extending longitudinally the seam to be welded,paired electrodes contacting with the material to be welded, saidelectrodes supported by said bars, insulating membersinterposed betweensaid electrodes and lsaid bars, said insulating members adapted to moveaxially of said bars, and means adapted to adjust the position of saidelectrodes on said bars.

16. In apparatus for electric welding, a frame,

supporting bars carried by said frame, said barsv extendinglongitudinally the seam to be welded, paired electrodes contacting withthe material to be welded, said electrodes supported by said bars,insulating members interposed between said electrodes and with saidbars, resilient means adapted to maintain contact between saidelectrodes and said material to be welded, and means adapted to adjustthe position oi said electrodes on said bars.

17. In apparatus for electric welding, a frame, paired electrodessupported inA said frame, and means for supporting the material to bewelded in contact with said electrodes, said means comprising a rollerreplacably assembled on a hingedly supported shaft.

18. In a device of the character described, a frame having sides made ofstructural shapes, a transverse plate joining the corresponding ends ofsaid sides, supporting bars extending substantially parallel with saidsides, electrodes adjustably mounted on said bars, means for adjustingthe position of said electrodes axially of said bars, and means forbringing into welding relationship with said electrodes a seam to bewelded.

19. In a device of the character described, a frame having substantiallyparallel side members, transversemembersjoining saidside members andtherewith forming an enclosure, supporting bars extending substantiallyvthrough said enclosure,

said bars supporting pairs of electrodes, means adapted to adjust theposition of said electrodes on said bars, and means for bringing thematerial to be welded into welding relationship with said electrodes.

20. In a device of the character described, a pair of iixed supportingbars extending longitudinally in a trame, blocks slidably carried onsaid bars, electrode members supported'by said blocks, means foradjusting the electrode members relative to said bars, and means foradvancing relative to said electrode members a seam to be welded.

21. In apparatus for welding elongated adjoining parts, a sealedenclosure adapted to retain a predetermined atmosphere, supportingmembers extending into said enclosure, heating elements withinsaidenclosure, said heating elements being carried by said supportingmembers, means independent of .the supporting members for adjusti ingthe position of said heating members on said supporting members, andmeans for supplying heating energy to said heating members,

\ said last `named means being sealed at its point of entrance to theenclosure to prevent a loss of the predetermined atmosphere.

22. In apparatus for welding adjoining'parts of a substantiallycylindrical article, a sealed enclosure adapted to retain apredetermined atmosphere, a supporting member extending into saidenclosure, an electric conducting member embracing a part of saidcylindrical article and being carried by said supporting member, saidconducting member being contained within said enclosure, means extendinginto s aid enclosure for supplying heating current to said conductingmember, and means associated with said last named means to prevent aloss of the predetermined atmosphere.

23. In apparatus for the fusion of abutting surfaces of a metal article,a pair of current conducting me bers embracing parts of the article, anenclosure surrounding the parts, a predetermined controlled atmospherewithin said enclosure and surrounding said surfaces, adjusting means forIadapted. to retain rent carrying means extending through a wall of Atheenclosure, and means for preventing a leakage of the predeterminedatmosphere at said wall.

25. In apparatus for welding an article, an enclosure surrounding a partof said article and adapted to retain a predetermined atmosphere,resilient means for bringing a surface of said article into weldingrelationship with another surface, an electricconducting memberembracing a part of said article, and a current carrying means forsupplying current to said conducting member, said current carrying meansextending through a wall of the enclosure.

26. In apparatus for welding an article, an enclosure surrounding a partof said article and adapted to retain a predetermined atmosphere,

means for bringing a surface of said article into contactingrelationship with another surface, a multiplicity of current conductingmembers within said enclosure, supporting means for said currentconducting members, said supporting means extending into the saidenclosure, and means for adjusting said current conducting members onsaid supporting means, said adjusting means extending through a wall ofthe aforesaid enclosure.

- 27. In apparatus for welding an article, an enclosure surrounding apart of said article and a predetermined atmosphere,

means for bringing a surface of said article into 'contactingrelationship with another surface, a

current conducting member embracing a part of said article, currentcarrying means for supplying current to said conducting member, saidcurrent carrying means extending through a wall of the enclosure, andmeans for simultaneously delivering into said enclosure two sources offluid comprising the aforesaid predetermined atmosphere.

28. In apparatus for welding an article, an enclosure surroundinga partof said article and adapted to retain a predetermined atmosphere, vmeansfor bringing a surface of said article into contacting relationship withanother surface, a current conducting member embracing a part of saidarticle, current carrying means for supplying current to said conductingmember, said current carrying means extending through a wall of theenclosure, delivering to the region of welding two sources of fluidcomprising the aforesaid controlled atmosphere.

29. In apparatus for welding an article, an enclosure surrounding a partof said article and adapted to retain a predetermined atmosphere, meansfor bringing a surface of said article into contacting relationship withanother surface, a multiplicity of current conducting members 'embracingparts of said article, current carrying means for supplying current tosaid conducting members, means for progressively moving the articlerelative to said current conducting members, and means for bringing thesurfaces into welding relationship.

l COURTNEY N. MITCHELL.

and means for simultaneously Y

